From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id D25A36B0012 for ; Thu, 30 Jun 2011 12:10:02 -0400 (EDT) MIME-Version: 1.0 Message-ID: Date: Thu, 30 Jun 2011 09:09:37 -0700 (PDT) From: Dan Magenheimer Subject: RE: frontswap/zcache: xvmalloc discussion References: <4E023F61.8080904@linux.vnet.ibm.com> <0a3a5959-5d8f-4f62-a879-34266922c59f@default 4E03B75A.9040203@linux.vnet.ibm.com 89b9d94d-27d1-4f51-ab7e-b2210b6b0eb5@default f6415652-5925-4aad-b8be-900ce3afd902@default> In-Reply-To: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Seth Jennings Cc: linux-mm , Nitin Gupta , Robert Jennings , Brian King , Greg Kroah-Hartman , Dave Hansen > FWIW, I've measured the distribution of zsize (pages compressed > with frontswap) on my favorite workload (kernel "make -j2" on > mem=3D512M to force lots of swapping) and the mean is small, close > to 1K (PAGE_SIZE/4). I've added some sysfs shows for both > the current and cumulative distribution (0-63 bytes, 64-127 > bytes, ..., 4032-4095 bytes) for the next update. >=20 > I tried your program on the text of Moby Dick and the mean > was still under 1500 bytes ((3*PAGE_SIZE)/8) with a good > broad distribution for zsize. Oops, on retry this morning, I am now clearly seeing the poor compression. Not sure what is different from last night, but I suspect I was "watch"ing the new sysfs output during massive swapping during the run of the test program and it wasn't updated until program completion (at which point I was no longer perusing the sysfs output). Sorry for the noise. However, now that I have a test case I am implementing another sysfs tunable to reject poorly- compressible pages that would drive the mean zsize above the tunable. Zcache will reject these pages until the mean falls below the threshold. (Setting it to PAGE_SIZE will continue current behavior, but I've set the default to (5*PAGE_SIZE)/8 for now.) Dan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org